feat(invites): team invite links — admin create/revoke, public accept (#42)

* feat(branding): white-label — public /branding, admin write, shell theming

app_settings branding.* keys (product name, logo/favicon URLs, accent
color, docs/support links). Public GET /branding so login and shell
theme pre-auth; admin writes via PUT /settings.

useBranding() applies document.title, accent CSS var and favicon;
BrandWordmark replaces hardcoded wordmarks; admin Platform settings
gain a Branding form. MCP containr_branding_get + settings_update.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat(invites): team invite links — admin create/revoke, public accept

Admins mint single-use invite links (sha256-hashed token at rest,
optional email binding, configurable TTL). Public endpoints let the
accept page validate the link and register — working even while
public signup is disabled.

- migration + sqlc queries/model for user_invites
- POST /admin/invites (returns one-time token+url), GET list, DELETE revoke
- GET /auth/invites/:token public validation, POST /auth/accept-invite
- CLI containr invites list|create|revoke; MCP invites tools
- /auth/accept-invite page (expired/used/invalid states, bound-email lock)
- Admin page Team invites section: create, copy link, revoke
- OpenAPI + generated types + CLI guide

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/routes.go

@@ -260,6 +260,11 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 			public.GET("/maintenance", handleMaintenancePage)
 			public.GET("/branding", handleGetBranding)
 
+			// Invite accept flow — validates the link, then registers
+			// even while public signup is closed.
+			public.GET("/auth/invites/:token", handleGetInvite)
+			public.POST("/auth/accept-invite", handleAcceptInvite)
+
 			// Wake callback for sleep-mode placeholders. Unauthenticated but
 			// non-destructive: it only reconciles the service back to running.
 			public.Any("/internal/wake/:id", handleServiceWake)
@@ -495,6 +500,11 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 			admin.POST("/admin/banners", handleAdminCreateBanner)
 			admin.PATCH("/admin/banners/:id", handleAdminUpdateBanner)
 			admin.DELETE("/admin/banners/:id", handleAdminDeleteBanner)
+
+			// Team invites — single-use registration links
+			admin.GET("/admin/invites", handleAdminListInvites)
+			admin.POST("/admin/invites", handleAdminCreateInvite)
+			admin.DELETE("/admin/invites/:id", handleAdminDeleteInvite)
 			admin.GET("/audit-logs", handleGetAuditLogs)
 			admin.GET("/audit-logs/:resource/:id", handleGetResourceAuditLogs)